Peroneal Tendon Dysfunction
Dislocating peroneal tendons are an uncommon injury to a group of two tendons whose muscles originate on the outside of the calves. These two muscles are named the Peroneus Brevis and Peroneus Longus. These two muscles are responsible for eversion of the foot. This movement of the foot is demonstrated by standing and then rolling to the outside of the foot. These tendons are also called “stirrup” tendons because as they pass into the foot they act as a stirrup to help hold up the arch of the foot. As these tendons pass behind the outside ankle bone, called the fibula, they are held in place by a band of tissue called the peroneal retinaculum. Injury to the retinaculum can cause it to stretch or even tear. When this occurs the peroneal tendons can dislocate from their groove on the back of the fibula. The tendons can be seen to roll over the outside of the fibula. This will cause the tendons to function abnormally and can cause damage to the tendons. Dislocating peroneal tendons most commonly occur as a result of injury during participation in athletic activities. The most common sport causing injury is snow skiing. It can also occur while playing football, basketball, and soccer. This injury can occur in non-athletes, as a result of a severe ankle sprain. The injury typically results in a popping or sharp pain on the outside of the ankle. The outside of the ankle is called the lateral malleolus. Commonly however, there may be little to no discomfort at the time of injury, which later becomes symptomatic.
Physical examination will reveal swelling behind the outside of the ankle if it is an acute injury. If the injury is chronic there may be little to no swelling. There is usually tenderness particularly when pressure is applied behind the outside of the ankle. Having the patient forcefully turn the foot outward against the physician’s hand can demonstrate dislocation of the peroneal tendons. This will cause the peroneal tendons to dislocate over the outer edge of the lateral malleolus.
X-rays and occasionally an MRI exam may be necessary to confirm the diagnosis. X-rays are commonly taken to ensure that there are not any other injuries to the bones of the foot and ankle. An MRI will provide your physician with information about abnormal positioning and/or possible tears of the peroneal tendons.
Non Surgical Treatment
If there is an acute injury the initial treatment is usually crutches with no weight being applied to the foot. Usually a splint or compressive wrap is applied to decrease swelling. Anti-inflammatory medications and ice are often utilized to help decrease swelling. Once the swelling has subsided your physician will be better able to tell the true extent of injury. Mild injury can be treated with conservative, non-surgical means. Mild injury results in stretching of the peroneal retinaculum without dislocation of the peroneal tendons. The patient is placed in a cast or removable cast boot and must use crutches for six weeks. During this time no weight can be applied to the foot. After six weeks the patient is re-examined. If the injury has not healed further treatment may be necessary.
Surgical correction is necessary in cases of failed conservative therapy and moderate to severe injuries. With moderate to severe injuries the peroneal retinaculum is either torn or severely stretched to a point that the peroneal tendons will easily dislocate. Surgery will involve tightening the stretched or torn peroneal retinaculum. Both absorbable and non-absorbable suture or stitches will be necessary to hold the tissue in place until it heals. This may require drill holes or metallic anchors to be placed in the fibula to aid in suturing the peroneal retinaculum back onto itself.
Twenty-five percent of the population does not have a groove on the back of the fibula for the peroneal tendons to move in. This groove is called the peroneal groove. This can be a causative factor for peroneal tendon dislocation and can only be identified at the time of surgery. If this is encountered during surgery a peroneal groove will be created by performing bone cuts in the back of the fibula. These may require bone screws or pins to hold the bone in place while it heals. During the surgery the peroneal tendons will be examined for possible tears or damage. If this is found it will be repaired by suture.
Post-operatively the patient is placed on crutches and in a splint or cast for 4 to 6 weeks with no weight being applied to the foot. This is followed by 2 to 4 weeks of protected weight bearing in a cast or removable cast boot. This is usually followed by 3 to 6 weeks of physical therapy to regain strength and motion.
Once an injury occurs it is always possible for a person to re-injure or re-dislocate their peroneal tendons. Surgical complications are rare but can include: infection, reoccurrence, stiffness and weakness of the peroneal tendons, and delay or failure of bone cuts in the fibula to heal. The risk for complications is greatly reduced by taking your prescriptions as instructed and strictly following post-operative instructions.